System Description [09/2015 - ]

1. The pre-collision system detects vehicles and obstacles in front of the vehicle and performs the following: 1) optimally uses system controls to avoid collisions, and 2) uses system controls to reduce impact during a collision.

1. Front collision detection
   1. The driving support ECU assembly receives information about vehicles and obstacles in front of the vehicle from the millimeter wave radar sensor assembly and object recognition camera. Then, based on vehicle speed, road conditions and obstacle location, the driving support ECU assembly determines, in advance, the risk of a collision and if a collision is unavoidable.
   2. The driver monitor camera detects the direction that the driver's head is facing and whether the driver's eyes are open or closed. When a potential collision is detected and the camera determines that the driver's head is not facing forward or that the driver's eyes are closed, it activates the pre-collision safety controls in advance.
2. Sudden braking detection
   1. The skid control ECU assembly activates the pre-collision seat belts when it detects sudden braking. Sudden braking is determined based on brake oil pressure and other information from the master cylinder pressure sensor.
3. Vehicle control impossible judgment
   1. The pre-collision seat belts are activated when it is determined that there is a high probability that the vehicle cannot be controlled. The judgment is based on vehicle stability information from the yaw rate sensor and steering angle sensor.
4. Component

   Component	Detection Content
   Millimeter wave radar sensor assembly	Front object
   Object recognition camera	Front object
   Driver monitor camera	Driver facial direction Driver eye opening level signal

1. When the system determines that there is a risk of colliding with an obstacle in front of the vehicle, the multi-information display and warning buzzer are used to warn the driver and help with collision avoidance.

1. When the system determines that a collision with an obstacle is unavoidable, that sudden braking has occurred, or that vehicle control is impossible, the system performs seat belt control. During seat belt control, slack in the seat belts is reduced to increase occupant restraint and aid the pretensioner.

1. When the system determines that there is a risk of colliding with an obstacle in front of the vehicle, brake assist is set to standby mode. Then, when the driver depresses the brake pedal, the hydraulic brake pressure is increased to improve braking effectiveness.

1. When it is determined that there is a risk of colliding with an obstacle in front of the vehicle, the AVS is operated to control the damping force, suppress nose diving and rolling, and support collision avoidance through steering.

1. When the system determines that there is a risk of colliding with an obstacle in front of the vehicle, the Variable Gear Ratio Steering (VGRS) system is set to standby at an optimum steering ratio (i.e., increasing power steering) for collision avoidance.

1. When it is determined that the obstacle in front cannot be avoided, collision avoidance support is performed by operating the brakes to reduce the speed at the time of the collision and lessen the impact. If the vehicle stops due to the operation of the pre-collision brakes, the brakes are maintained for up to 2 seconds and then automatically released. After the vehicle stops, the pre-collision brakes can be released by depressing the accelerator or brake pedal.

1. When the pre-collision brake cancel switch in the No. 1 instrument panel under cover sub-assembly is turned ON, the pre-collision alarm, pre-collision alarm brake and pre-collision brake do not operate.

   HINT: 

   While the pre-collision brake cancel switch is ON, the combination meter's PCS indicator light tuns ons.

1. When the VSC off switch is turned on, the pre-collision brake assist and pre-collision brake do not operate.

   HINT: 

   After the VSC off switch is pressed, the PCS indicator illuminates and "Pre-collision brakes are disabled because VSC is OFF" is displayed in the multi-information display in the combination meter for 6 seconds.

HINT: 

• ◦: Operation
• X: Not operation
• *1: Inoperative parts are different depending on malfunction areas
• *2: Only operates when seat belt is fastened
• *3: Pre-collision seat belts may operate when brakes are suddenly applied
• *4: This function operates only for vehicles equipped with an object recognition camera.

1. When the millimeter wave radar sensor assembly and object recognition camera detect an object in front of the vehicle under the conditions described below, the driving support ECU assembly may determine that a collision is unavoidable, and activates the pre-collision system. However, this is not abnormal.
   Fig 1: Wave Radar Sensor Assembly & Object Recognition Camera Chart

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   HINT: 

   • The pre-collision system does not activate when the pre-collision sensor detects safety cones and other plastic objects.
   • The pre-collision system may or may not activate when the pre-collision sensor detects the following objects: people, bicycles, motorcycles, trees, animals and snow fences.

   Object Type	Example
   Object that cannot be detected	Plastic items (safety cones)
   Object that cannot always be detected	Bicycles, motorcycles, trees, animals, snow fences, etc.